diff --git a/main.cpp b/main.cpp
index 7a8b49a..57efd33 100644
--- a/main.cpp
+++ b/main.cpp
@@ -21,7 +21,7 @@ void help()
 #endif
     <<"nasal <option>\n"
     <<"option:\n"
-    <<"    -h, --help      | get help.\n"
+    <<"    -h, --help      | get this help.\n"
     <<"    -v, --version   | get version of nasal interpreter.\n\n"
     <<"nasal <file>\n"
     <<"file:\n"
@@ -102,12 +102,9 @@ void execute(const string& file,const std::vector<string>& argv,const u32 cmd)
     if(cmd&VM_CODEINFO)
         gen.print();
     
-    // run bytecode
+    // run
     if(cmd&VM_DEBUG)
-    {
-        nasal_dbg debugger(nerr);
-        debugger.run(gen,linker,argv,cmd&VM_OPCALLNUM);
-    }
+        nasal_dbg(nerr).run(gen,linker,argv,cmd&VM_OPCALLNUM);
     else if(cmd&VM_EXECTIME)
     {
         auto start=std::chrono::high_resolution_clock::now();
diff --git a/nasal_dbg.h b/nasal_dbg.h
index 4ebc729..e04f7d2 100644
--- a/nasal_dbg.h
+++ b/nasal_dbg.h
@@ -248,7 +248,7 @@ void nasal_dbg::run(
     typedef void (nasal_dbg::*nafunc)();
     const nafunc oprs[]=
     {
-        nullptr,                &nasal_dbg::o_intg,
+        nullptr,              &nasal_dbg::o_intg,
         &nasal_dbg::o_intl,   &nasal_dbg::o_loadg,
         &nasal_dbg::o_loadl,  &nasal_dbg::o_loadu,
         &nasal_dbg::o_pnum,   &nasal_dbg::o_pnil,
diff --git a/nasal_vm.h b/nasal_vm.h
index 8c339da..67a0a67 100644
--- a/nasal_vm.h
+++ b/nasal_vm.h
@@ -893,20 +893,20 @@ inline void nasal_vm::o_mcallh()
 }
 inline void nasal_vm::o_ret()
 {
-/*  +-----------------+
-*   | return value    | <- top[0]
-*   +-----------------+
-*   | old pc          | <- top[-1]
-*   +-----------------+
-*   | old localr      | <- top[-2]
-*   +-----------------+
-*   | old upvalr      | <- top[-3]
-*   +-----------------+
-*   | local scope     |
-*   | ...             |
-*   +-----------------+ <- local pointer stored in localr
-*   | old funcr       | <- old function stored in funcr
-*   +-----------------+
+/*  +-------------+
+*   | return value| <- top[0]
+*   +-------------+
+*   | old pc      | <- top[-1]
+*   +-------------+
+*   | old localr  | <- top[-2]
+*   +-------------+
+*   | old upvalr  | <- top[-3]
+*   +-------------+
+*   | local scope |
+*   | ...         |
+*   +-------------+ <- local pointer stored in localr
+*   | old funcr   | <- old function stored in funcr
+*   +-------------+
 */
     nas_ref  ret  =top[0];
     nas_ref* local=localr;
@@ -930,7 +930,7 @@ inline void nasal_vm::o_ret()
         for(u32 i=0;i<size;++i)
             upval.elems.push_back(local[i]);
     }
-    // cannot use gc.coroutine to judge,
+    // cannot use gc.cort to judge,
     // because there maybe another function call inside
     if(!pc)
         gc.ctxreserve();